RandyS

I have to replace the piece of Resistor Wire from the firewall to the coil on my 66 442. I am unable to locate any of the correct wire locally. Can anyone tell me what what resistance (in Ohms) that wire provides? If I can find that out, I can just wire one in series.
Thanks,
Randy

oldcutlass

I bet one of those ignition resistors is pretty close.

http://www.summitracing.com/parts/MAA-700/

RandyS

Hmm, you are probably right. 1.5 ohms isn't going to drop much current, almost not worth fooling with it.

oddball

It *is* worth it if running points. It drops the positive side of the coil to 7 to 9 volts. Higher will burn the points.
It needs to be a large power resistor, not a typical 1/4 watt resistor. The ignition will pull several amps while running.

MDchanic

A run-of-the-mill Mopar ignition resistor like this ought to work fine:



It's Standard Automotive Products #RU-12 in any lookup.

Advance has 'em for four bucks. Other suppliers should be similar.

If you want to be sure it's right, just check the voltage at the (+) coil terminal when it's running to confirm it's about 8 volts.

- Eric

Ozzie

The 1966 Oldsmobile Chassis Service Manual, in both the wiring diagram and the specifications, show a value, for the 8 cylinder vehicles, of 1.35 ohms at 80 degrees F for the resistance wire. (There is an additional 1.77-2.05 ohms in the primary winding of the coil.) As has been mentioned, be sure to calculate the required heat dissipation accurately. The wire dissipated its heat over its entire length. The old V=IR and W=VI ought to get it as long as the correct values are used.

MDchanic

The RU-12 unit I posted is made of ceramic, and designed to dissipate heat properly.

I will admit that I can't find its resistance spec. anywhere, but Standard also makes an RU-10, RU-11, and RU-13 (and a few others, I believe), and these should be on the shelf at most parts stores, so you could always bring your ohm meter to confirm the proper resistance (and it doesn't have to be exact - these sorts of components usually have a 10-20% tolerance band).

- Eric

RandyS

I ended up swapping the resistance wire from another car (that actually has HEI, and should not use the resistance wire) to this car. Problem solved!
Thanks for all of your suggestions!

oldcutlass

And that will work also.